Variable valve lift may be used in engines to increase efficiency and decrease emissions over a wide range of engine operating conditions. For instance, a cylinder valve lift magnitude and/or opening/closing duration may be altered via a valve adjustment system based on various engine operating conditions, such as engine temperature, fuel injection magnitude/timing, engine load, engine speed, requested torque, etc. It may also be desirable to deactivate selected cylinders via a valve adjustment system during certain engine operating conditions to increase engine efficiency, decreases emissions, and/or decrease fuel usage. For instance, cylinder valves corresponding to a cylinder may be deactivated during engine idle or low engine speeds.
However, valve systems with variable valve lift functionality may include complicated hydraulic sub-systems as well as other control sub-systems which may use a large amount of energy in the engine, thereby subverting some of the efficiencies achieved through valve lift adjustment. Thus, the energy used by the valve system may offset some of the efficiencies achieved via the variation in valve lift.
As such in one approach, a cylinder valve system in an engine is provided. The cylinder valve system includes a first oil pressurized bore corresponding to a cylinder valve and in fluidic communication with a control valve assembly, the control valve assembly comprising at least one hydraulic valve. The cylinder valve system further includes a second oil pressurized bore corresponding to the cylinder valve and in fluidic communication with the control valve assembly. Adjustment of the oil pressure in the first and second bores enables cylinder valve profile adjustment. In this way, multiple hydraulic bores may be incorporated into a valve system to enable valve lift magnitude and/or opening/closing duration adjustment as well as cylinder valve deactivation, if desired.
In one example, a lash adjuster may be positioned in the second oil pressurized bore and a valve stem and valve spring may be positioned in the first oil pressurized bore, the valve stem mechanically coupled to the lash adjuster. In this way, hydraulic force on both the valve stem and the lash adjuster may be independently adjusted via the control valve assembly to enable valve lift profile control.
Further in one example, the oil pressure in the first and/or second pressurized bores may be altered to inhibit valve stem movement in the valve assembly, to deactivate the cylinder valve. Specifically, in one example, oil from an active cylinder may be transferred to the first oil pressurized bore to inhibit activation. In this way, hydraulic motion from an active cylinder valve may be used to deactivate another cylinder valve. As a result, the efficiency of the valve system is increased while decreasing engine fuel usage through cylinder deactivation.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.